I have an Acer Aspire ES-15. When I plug a Jack to the laptop (On windows 10) Came up a window where I can select if the device i pluged in is a microphone, a headphone or a speaker. (My audio card is a Realtek HD audio) Now I have only Ubuntu for OS and my PC does not recognize if I connect a microphone to the only jack port that has.
Maybe give this a try...
- Install pavucontrol: sudo apt-get install pavucontrol
- Run: sudo pavucontrol
- Go to the "Input Devices" tab
- Click the lock icon to unlock the channels
- Under "Port", select the correct microphone (front or rear)
Found in this thread here: Sound Input device (microphone) not working